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Abstract:

A process for making ethylbenzene and/or styrene by reacting toluene with
methane is disclosed. In one embodiment the process can include reacting
toluene with methane to form a product stream comprising ethylbenzene and
further processing the ethylbenzene to form styrene in an existing
styrene production facility.

Claims:

1-20. (canceled)

21. A system for producing ethyl benzene comprising: a first reactor,
wherein the first reactor is adapted to react toluene to form methane to
form an output stream comprising ethylbenzene or styrene; an existing
styrene production facility, wherein the output stream from the first
reactor is fluidically connected to the existing styrene production
facility.

22. The system of claim 21, wherein the existing styrene production
facility comprises: a separation apparatus adapted to remove at least a
portion of any benzene from the first product stream; an alkylation
reactor adapted to form ethylbenzene by reacting benzene and
polyethylbenzene, wherein the alkylation reactor is in fluidic connection
with the separation apparatus; and a dehydrogenation reactor adapted to
form styrene by dehydrogenating ethylbenzene, wherein the
dehydrogentation reactor is in fluidic connection with the separation
apparatus.

23. The system of claim 21, wherein the first reactor comprises one or
more single or multi-stage catalyst beds containing a catalyst.

24. The system of claim 23, wherein the catalyst is a metal oxide.

25. The system of claim 23, wherein the catalyst is a zeolite.

26. The system of claim 25, wherein the zeolite is a base zeolite
selected from the group consisting of an X, Y, mordenite, ZSM, silicalite
or AIPO4-5 zeolite.

27. The system of claim 21 wherein the first reactor further comprises a
cooling system.

28. The system of claim 27, wherein the cooling system is an external
cooling jacket, internal cooling coils, or an external heat exchanger.

29. The system of claim 21, wherein the first reactor is a Lurgi molten
salt type reactor.

30. The system of claim 21, wherein the first reactor is a vapor phase
reactor.

31. The system of claim 21, further comprising a second reactor in series
with the first reactor.

32. The system of claim 21 further comprising an oxygen addition system,
wherein the oxygen addition system is adapted to add oxygen to the first
and second reactors so as to maintain the oxygen content in each reactor
within a predetermined range.

33. The system of claim 21, further comprising a second reactor in series
with the first reactor.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to a process for the production of
ethylbenzene and styrene.

[0003] 2. Description of the Related Art

[0004] Styrene is an important monomer used in the manufacture of many of
todays plastics. Styrene is commonly produced by making ethylbenzene,
which is then dehydrogenated to produce styrene. Ethylbenzene is
typically formed by one or more aromatic conversion processes involving
the alkylation of benzene.

[0005] Aromatic conversion processes, which are typically carried out
utilizing a molecular sieve type catalyst, are well known in the chemical
processing industry. Such aromatic conversion processes include the
alkylation of aromatic compounds such as benzene with ethylene to produce
alkyl aromatics such as ethylbenzene. Typically an alkylation reactor,
which can produce a mixture of monoalkyl and polyalkyl benzenes, will be
coupled with a transalkylation reactor for the conversion of polyalkyl
benzenes to monoalkyl benzenes. The transalkylation process is operated
under conditions to cause disproportionation of the polyalkylated
aromatic fraction, which can produce a product having an enhanced
ethylbenzene content and a reduced polyalkylated content. When both
alkylation and transalkylation processes are used, two separate reactors,
each with its own catalyst, can be employed for each of the processes.
The alkylation and transalkylation conversion processes can be carried
out in the liquid phase, in the vapor phase, or under conditions in which
both liquid and vapor phases are present, and combinations thereof.

[0006] In the formation of ethylbenzene from alkylation reactions of
ethylene and benzene, impurities and undesirable side products may be
formed in addition to the desired ethylbenzene. These undesirable
products can include such compounds as xylene, cumene, n-propylbenzene
and butylbenzene, as well as polyethylbenzenes, and high boiling point
alkyl aromatic components, sometimes referred to as "heavies," having a
boiling point at or above 185° C. As can be expected, reduction of
these impurities and side products is important. This is especially true
in the case of xylene, particularly the meta and para xylenes, which have
boiling points that are close to that of ethylbenzene and can make
product separation and purification difficult.

[0007] Ethylene is obtained predominantly from the thermal cracking of
hydrocarbons, such as ethane, propane, butane, or naphtha. Ethylene can
also be produced and recovered from various refinery processes. Ethylene
from these sources can include a variety of undesired products, including
diolefins and acetylene, which can act to reduce the effectiveness of
alkylation catalysts and can be costly to separate from the ethylene.
Separation methods can include, for example, extractive distillation and
selective hydrogenation of the acetylene back to ethylene. Thermal
cracking and separation technologies for the production of relatively
pure ethylene can account for a significant portion of the total
ethylbenzene production costs.

[0008] Benzene can be obtained from the hydrodealkylation of toluene which
involves heating a mixture of toluene with excess hydrogen to elevated
temperatures (for example 500° C. to 600° C.) in the
presence of a catalyst. Under these conditions, toluene can undergo
dealkylation according to the chemical equation:
C6H5CH.sub.3+H2→C6H6+CH4 This
reaction requires energy input and as can be seen from the above
equation, produces methane as a byproduct, which is typically separated
and may used as heating fuel for the process.

[0009] In view of the above, it would be desirable to have a process of
producing ethylbenzene, and styrene, which does not rely on thermal
crackers and expensive separation technologies as a source of ethylene.
It would also be desirable if the process was not dependent upon ethyene
from refinery streams that contain impurities which can lower the
effectiveness and can contaminate the alkylation catalyst. It would
further be desirable to avoid the process of converting toluene to
benzene with its inherent expense and loss of a carbon atom to form
methane.

SUMMARY

[0010] One embodiment of the present invention is a process for making
ethylbenzene which involves reacting toluene and methane in one or more
reactors to form a first product stream comprising ethylbenzene and/or
styrene and then further processing at least a portion of the components
of the first product stream in at least a portion of an existing styrene
production facility. The first product stream may also contain one or
more of benzene, toluene, or methane. The process may comprise at least
one separation apparatus for at least partial separation of the
components from the first product stream. The reactors can include a
reaction zone capable of dissipating heat to maintain the reaction zone
within a desired temperature range for reacting toluene and methane to
form ethylbenzene and/or styrene.

[0011] Methane may be separated from the first product stream creating a
second product stream having reduced methane content. The methane may be
recycled back to the reactors or may be utilized as heating fuel within
the process. Toluene may also be separated from the first product stream
and recycled to the reactors. At least a portion of the components of the
first product stream can be further processed in a styrene production
process. The styrene production process can include an alkylation reactor
to form ethylbenzene by reacting benzene and ethylene, and a
dehydrogenation reactor to form styrene by dehydrogenating ethylbenzene.

[0012] Yet another embodiment of the present invention is a process for
making ethylbenzene and/or styrene which includes reacting toluene and
methane in one or more reactors to form a first product stream comprising
one or more of ethylbenzene, styrene, benzene, toluene, and methane;
removing at least a portion of any methane from the first product stream
to form a second product stream with reduced methane content; separation
of at least a portion of the benzene from the first or second product
stream; reacting at least a portion of the separated benzene in an
alkylation reactor to form ethylbenzene; and dehydrogenating the
ethylbenzene in one or more dehydration reactors to form styrene. At
least a portion of one or more of the separation, alkylation, and
dehydrogenation processes are performed utilizing the facilities of an
existing styrene production facility. The one or more reactors may have
one or more reaction zones and be capable of dissipating heat to maintain
one or more of the reaction zones within the desired temperature range(s)
to promote the reaction of toluene and methane to form ethylbenzene.

[0013] A further embodiment of the invention is a method for revamping an
existing styrene production facility by adding a process for reacting
toluene with methane to produce a new product stream containing
ethylbenzene and styrene. The new product stream containing ethylbenzene
and styrene may then be sent to the existing styrene production facility
for further processing to form additional styrene. The existing styrene
production facility can include a separation apparatus to remove at least
a portion of any benzene and toluene from the new product stream, an
alkylation reactor to form ethylbenzene by reacting the benzene and
ethylene, and a dehydrogenation reactor to form styrene by
dehydrogenating ethylbenzene.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic block diagram illustrating a process for
making ethylbenzene and styrene; and

[0015] FIG. 2 is a schematic block diagram illustrating a process for
making ethylbenzene and styrene according to an embodiment of the present
invention.

DETAILED DESCRIPTION

[0016] Turning now to the drawings and referring first to FIG. 1, there is
illustrated a schematic block diagram of one embodiment of an
alkylation/transalkylation process carried out in accordance with the
prior art. A feed stream of toluene is supplied via line 10 to reactive
zone 100 which produces product streams of methane via line 12 and
benzene via line 14. The benzene via line 14 along with ethylene via line
16 are supplied to an alkylation reactive zone 120 which produces
ethylbenzene and other products which are sent via line 18 to a
separation zone 140. The separation zone 140 can remove benzene via line
20 and send it to a transalkylation reaction zone 160. The benzene can
also be partially recycled via line 22 to the alkylation reactive zone
120. The separation zone 140 can also remove polyethylbenzenes via line
26 which are sent to the transalkylation reaction zone 160 to produce a
product with increased ethylbenzene content that can be sent via line 30
to the separation zone 140. Other byproducts can be removed from the
separation zone 140 as shown by line 32, this can include methane and
other hydrocarbons that can be recycled within the process, used as fuel
gas, flared, or otherwise disposed of. Ethylbenzene can be removed from
the separation zone 140 via line 34 and sent to a dehydrogenation zone
180 to produce styrene product that can be removed via line 36.

[0017] The front end of the process 300, designated by the dashed line,
includes the initial toluene to benzene reactive zone 110 and the
alkylation reactive zone 120. It can be seen that the input streams to
the front end 300 can include toluene via line 10 and ethylene via line
16 and oxygen via line 15. There can also be input streams of benzene
from alternate sources other than from a toluene reaction, shown as
reactive zone 100, although they are not shown in this embodiment. The
output streams include the methane via line 12 which is produced during
the conversion of toluene to benzene in reactive zone 110 and the product
stream containing ethylbenzene via line 18 that is sent to the back end
of the process 400. The back end 400 includes the separation zone 140,
the transalkylation reaction zone 160 and the dehydrogenation zone 180.

[0018] Turning now to FIG. 2, there is illustrated a schematic block
diagram of one embodiment of the present invention. Feed streams of
toluene supplied via line 210 and methane supplied via line 216 are
supplied to a reactive zone 200, which produces ethylbenzene along with
other products, which can include styrene. In some embodiments an input
stream of oxygen 215 may be supplied to the reactive zone 200. The output
from the reactive zone 200 includes a product containing ethylbenzene,
which is supplied via line 218 to a separation zone 240. The separation
zone 240 can separate benzene that may be present via line 220 which can
be sent to an alkylation reaction zone 260. The alkylation reaction zone
260 can include a transalkylation zone. The separation zone 240 can also
remove heavy molecules that may be present via line 226. The alkylation
reaction zone 260 can produce a product with increased ethylbenzene
content that can be sent via line 230 to the separation zone 240. Other
byproducts can be removed from the separation zone 240 as shown by line
232, this can include methane and other hydrocarbons that can be recycled
within the process, used as fuel gas, flared or otherwise disposed of.
Ethylbenzene can be removed from the separation zone 240 via line 234 and
sent to a dehydrogenation zone 280 to produce styrene product that can be
removed via line 236. Any styrene that is produced from the reactive zone
200 can be separated in the separation zone 240 and sent to the
dehydrogenation zone 280 via line 234 along with the ethylbenzene product
stream, or can be separated as its own product stream, (not shown),
bypassing the dehydrogenation zone 280 and added to the styrene product
in line 236.

[0019] The front end of the process 500 includes the initial toluene and
methane reactive zone 200. The input streams to the front end 500 are
toluene via line 210 and methane via line 216 and optionally oxygen via
line 215. The output stream is the product containing ethylbenzene via
line 218 that is sent to the back end of the process 600. The back end
600 includes the separation zone 240, the alkylation reaction zone 260,
and the dehydrogenation zone 280.

[0020] A comparison of the front end 300 of the prior art shown in FIG. 1
against the front end 500 of the embodiment of the invention shown in
FIG. 2 can illustrate some of the features of the present invention. The
front end 500 of the embodiment of the invention shown in FIG. 2 has a
single reactive zone 200 rather than the two reactive zones contained
within the front end 300 shown in FIG. 1, the reactive zone 100, and the
alkylation reactive zone 120. The reduction of one reactive zone can have
a potential cost savings and can simplify the operational considerations
of the process.

[0021] Both front ends have an input stream of toluene, shown as lines 10
and 210. The prior art of FIG I has an input stream of ethylene 16 and a
byproduct stream of methane 12. The embodiment of the invention shown in
FIG. 2 has an input stream of methane 216. The feed stream of ethylene 16
is replaced by the feed stream of methane 216, which is typically a lower
value commodity, and should result in a cost savings. Rather than
generating methane as a byproduct 12 which would have to be separated,
handled and disposed of, the present invention utilizes methane as a
feedstock 216 to the reaction zone 200.

[0022] A comparison of the back end 400 of the prior art shown in FIG. 1
with the back end 600 of the embodiment of the invention shown in FIG. 2
can further illustrate the features of the present invention. It can be
seen that the back end 400 of the prior art shown in FIG. 1 is
essentially the same as the back end 600 of the embodiment of the
invention shown in FIG. 2. They each contain a separation zone, an
alkylation reaction zone, a dehydrogenation zone, and are interconnected
in the same or essentially the same manner. This aspect of the present
invention can enable the front end of a facility to be modified in a
manner consistent with the invention, while the back end remains
essentially unchanged. A revamp of an existing ethylbenzene or styrene
production facility can be accomplished by installing a new front end or
modifying an existing front end in a manner consistent with the invention
and delivering the product of the altered front end to the existing back
end of the facility to complete the process in essentially the same
manner as before. The ability to revamp an existing facility and convert
from a toluene/ethylene feedstock to a toluene/methane feedstock by the
modification of the front end of the facility while retaining the
existing back end can have significant economic advantages.

[0023] The reactive zone 200 of the present invention can comprise one or
more single or multi-stage reactors. In one embodiment the reactive zone
200 can have a plurality of series-connected reactors. Additionally and
in the alternative the reactive zones can be arranged in a parallel
manner. There can also be embodiments having multiple series-connected
reactors that are arranged in a parallel manner. The reactive zone 200
can be operated at temperature and pressure conditions to enable the
reaction of methane and toluene to form ethylbenzene, and at a feed rate
to provide a space velocity enhancing ethylbenzene production while
retarding the production of xylene or other undesirable products. The
reactive zone 200 can be operated in the vapor phase. One embodiment can
be operated in the vapor phase within a pressure range of atmospheric to
1000 psig. Another embodiment can be operated in the vapor phase within a
pressure range of atmospheric to 500 psig. Another embodiment can be
operated in the vapor phase within a pressure range of atmospheric to 300
psig. Another embodiment can be operated in the vapor phase within a
pressure range of atmospheric to 150 psig.

[0024] The feed streams of methane and toluene can be supplied to the
reactive zone 200 in ratios of from 2:1 moles of methane:moles of toluene
to 50:1 moles of methane:moles of toluene. In one embodiment the ratios
can range from 5:1 moles of methane:moles of toluene to 30:1 moles of
methane:moles of toluene. The reactants, toluene and methane, can be
added to the plurality of series-connected reactors in a manner to
enhance ethylbenzene production while retarding the production of
undesirable products. For example toluene and/or methane can be added to
any of the plurality of series-connected reactors as needed to enhance
ethylbenzene production.

[0025] In an embodiment of the invention oxygen is added to the reactive
zone 200 in amounts that can facilitate the conversion of toluene and
methane to ethylbenzene and styrene. The oxygen content can range from 1%
to 50% by volume relative to the methane content. In another embodiment
the desirable oxygen content can range from 2% to 30% by volume relative
to the methane content. In an embodiment of the invention, the reactor of
the present invention can comprise multiple reactors and oxygen can be
added to the plurality of series-connected reactors in a manner to
enhance ethylbenzene and/or styrene production while retarding the
production of undesirable products. Oxygen can be added incrementally to
each of the plurality of series-connected reactors as needed to enhance
ethylbenzene and/or styrene production, to limit the exotherm from each
of the reactors, to maintain the oxygen content within a certain range
throughout the plurality of reactors or to customize the oxygen content
throughout the plurality of reactors. In one embodiment there is the
ability to have an increased or reduced oxygen content as the reaction
progresses and the ethylbenzene and/or styrene fraction increases while
the toluene and methane fractions decrease. There can be multiple
series-connected reactors that are arranged in a parallel manner, which
can increase overall production capacity and provide for auxiliary
reactors to facilitate maintenance and/or regeneration activities.

[0026] The oxygen can react with a portion of the methane and result in an
exothermic reaction. The heat generated by the exothermic reaction can be
dissipated in many ways, such as for example utilizing an external
cooling jacket, internal cooling coils, heat exchange, or by using a
reactor such as a Lurgi molten salt type reactor. The heat removal can be
controlled in such a manner as to maintain the reaction within a desired
temperature range to facilitate the conversion of toluene and methane to
ethylbenzene and/or styrene. In an embodiment, the desirable temperature
range is from 550° C. to 1000° C. In another embodiment,
the desirable temperature range is from 600° C. to 800° C.
The heat generated by the exothermic reaction can be removed and
recovered to be utilized within the process.

[0027] In one embodiment the reactive zone 200 of the present invention
can comprise one or more single or multi-stage catalyst beds containing
catalyst(s). The catalyst that can be used in the reactive zone 200 can
include any catalyst that can couple toluene and methane to make
ethylbenzene and/or styrene and are not limited to any particular type.
It is believed that the oxidation reaction of toluene and methane can be
accelerated by base catalysis. In one non-limiting example the catalyst
can comprise one or more metal oxides. In one non-limiting example the
catalyst can contain a metal oxide that is supported on an appropriate
substrate. It is believed that with a metal oxide catalyst, the
oxygen/oxide sites can function as the active reaction centers, which can
remove hydrogen atoms from the methane to form methyl radicals and from
the toluene to form benzyl radicals. The C8 hydrocarbons can be
formed as a result of cross-coupling between the resulting methyl and
benzyl radicals. The catalysts may contain different combinations of
alkali, alkaline earth, rare earth, and/or transition metal oxides. In
another non-limiting example, the catalyst can comprise a modified basic
zeolite. In yet another non-limiting example the catalyst can be a base
zeolite, such as an X, Y, mordenite, ZSM, silicalite or AIPO4-5 that can
be modified with molybdenum, sodium, or other basic ions. The zeolite
catalyst may or may not contain one of more metal oxides.

[0028] The foregoing description of certain embodiments of the present
invention have been presented for purposes of illustration and
description. It is not intended to be exhaustive or limit the invention
to the precise form disclosed, and other and further embodiments of the
invention may be devised without departing from the basic scope thereof.
It is intended that the scope of the invention be defined by the
accompanying claims and their equivalents.